JP5873770B2 - Oxygen-absorbing resin composition and packaging material using the same - Google Patents

Description

  The present invention relates to an oxygen-absorbing resin composition and a packaging material using the same.

  A gas barrier resin such as an ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as “EVOH”) is a material excellent in oxygen gas barrier properties and carbon dioxide gas barrier properties. Since such a resin can be melt-molded, it can be laminated with a layer of thermoplastic resin (polyolefin, polyester, etc.) excellent in moisture resistance, mechanical properties, etc., and the resulting multilayer plastic is suitable as a packaging material It is used. However, the gas permeability of these gas barrier resins is not zero, and allows a non-negligible amount of gas to pass therethrough. In order to reduce such gas permeation, especially oxygen gas permeation which greatly affects the quality of the contents, and to remove oxygen gas already present inside the package at the time of packaging the contents. It is known to use oxygen absorbers.

  For example, a composition containing a transition metal catalyst and an ethylenically unsaturated compound (oxidizable resin) as an oxygen absorbent has been proposed (see JP-A-5-115777). In addition, resin compositions containing EVOH and an oxygen absorbent have been proposed (see JP 2001-106866 A, JP 2001-106920 A, and JP 2002-146217 A). Since the resin composition containing EVOH can be melt-molded similarly to EVOH, it can be suitably used for various packaging materials.

  However, when the oxygen absorbent or the oxygen-absorbing composition as described above is used as a packaging material, the oxygen absorbent is decomposed as oxygen absorption proceeds, and an unpleasant odor may be generated. For this reason, further improvements have been desired in applications where fragrance is important. In order to solve such a problem, a resin composition using a resin having a double bond only in the main chain has been disclosed (see International Publication WO2007-126157).

  However, the resin composition described in WO2007-126157 has a problem that fatty acids having 1 to 7 carbon atoms, which are odor components, are still generated due to oxygen absorption. As a method for removing fatty acids having 1 to 7 carbon atoms, multilayering with a deodorant layer has been proposed (Japanese Patent Laid-Open No. 2011-152788).

Japanese Patent Laid-Open No. 5-115776 JP 2001-106866 A JP 2001-106920 A JP 2002-146217 A International Publication WO2007-126157 JP 2011-152788 A

  However, the method described in Japanese Patent Application Laid-Open No. 2011-152788 has problems that the package becomes opaque or the oxygen absorbability is reduced. In food packaging materials, low odor, safety, and transparency that are even better than conventional products are demanded. Particularly in recent years, the demand for retort packaging materials has increased. There is a need for an oxygen-absorbing composition that does not generate an unpleasant odor even when processed under harsh conditions such as retort processing and can quickly remove residual oxygen in the packaging material.

  Under such circumstances, one of the objects of the present invention is to provide a resin composition having excellent oxygen absorbability and generating less odor due to oxygen absorption.

  Until now, the relationship between the double bond interval in the oxidizable resin and the decomposition product after oxygen absorption has not been studied in detail. As a result of diligent research to solve the above problems, the present inventors have found that the fatty acid generated during oxygen absorption is increased in molecular weight by increasing the interval between adjacent carbon-carbon double bonds. . And it discovered that the volatility of a fatty acid fell by high molecular weight formation, and the odor after oxygen absorption fell. Moreover, it discovered that elution of the fatty acid to water was suppressed by hydrophobizing the generated fatty acid, and there was an advantage in applications such as retort. The present invention is an invention based on these new findings.

  That is, the resin composition of the present invention is an oxygen-absorbing resin composition containing a thermoplastic resin and a transition metal salt, wherein the thermoplastic resin contains a plurality of carbon-carbon double bonds. In the thermoplastic resin containing a carbon chain as a main chain, the average number of carbon atoms existing between adjacent carbon-carbon double bonds is in the range of 7-13.

  The packaging material of the present invention includes a layer made of the resin composition of the present invention.

  According to the present invention, it is possible to obtain a resin composition having excellent oxygen absorbability and less odor generation due to oxygen absorption. Furthermore, according to the present invention, it is possible to obtain a resin composition that generates less unpleasant odor even when a treatment (such as a retort treatment) is performed in the presence of hot water. By using the resin composition of the present invention, a packaging material having excellent characteristics can be obtained.

  Hereinafter, embodiments of the present invention will be described. In the following description, specific materials and specific numerical ranges may be exemplified, but the present invention is not limited to these examples as long as the effects of the present invention are obtained. Moreover, as long as there is no description in particular, the material illustrated may be used individually by 1 type, and may use 2 or more types together.

  The resin composition of the present invention contains a thermoplastic resin (hereinafter sometimes referred to as “thermoplastic resin (A)”) and a transition metal salt (hereinafter sometimes referred to as “transition metal salt (B)”). It is an oxygen-absorbing resin composition.

(1.1) Structure and properties of thermoplastic resin (A) The thermoplastic resin (A) includes an unsaturated carbon chain containing a plurality of carbon-carbon double bonds as a main chain. Hereinafter, the unsaturated carbon chain may be referred to as “unsaturated carbon chain (U)”. In the thermoplastic resin (A), the average number of carbon atoms present between adjacent carbon-carbon double bonds is in the range of 7-13. Hereinafter, a carbon chain connecting adjacent carbon-carbon double bonds may be referred to as “carbon chain (C)”. Further, the number of carbon atoms existing between adjacent carbon-carbon double bonds (that is, the number of carbon atoms constituting the carbon chain (C)) may be referred to as “carbon number n”. The number of carbon atoms contained in the functional group bonded to the carbon chain (C) and the side chain bonded to the carbon chain (C) is not included in the carbon number n. In the thermoplastic resin (A), adjacent carbon-carbon double bonds are separated by a carbon chain (C) having n carbon atoms. Further, the thermoplastic resin (A) may be a macrocyclic polymer in which the main chain constitutes a high molecular weight ring.

  The thermoplastic resin (A) includes a resin in which a side chain or a functional group is bonded to a linear unsaturated carbon chain (U). Moreover, there is no limitation in particular in the structure of the both ends of an unsaturated carbon chain (U), and atoms other than a carbon atom may couple | bond with the both ends of an unsaturated carbon chain (U). However, it is necessary to select a side chain, a functional group, and a terminal group that are bonded to the unsaturated carbon chain (U) so as not to generate a problematic amount of unpleasant odor. For example, when a side chain containing a carbon-carbon double bond is bonded to an unsaturated carbon chain (U), adjacent carbon-carbon doubles in total including the unsaturated carbon chain (U) and the side chain. The average number of carbons n present between the bonds is in the range of 7-13.

  The average of carbon number n may exist in the range of 8-13 (for example, the range of 8-10). Moreover, carbon number n of all the carbon chains (C) may exist in the range of 7-13 (for example, the range of 8-13 or 8-10). The carbon number n can be measured by, for example, the ozonolysis GPC method.

  Since the thermoplastic resin (A) has a carbon-carbon double bond in its molecule, it can efficiently react with oxygen, and as a result, an oxygen scavenging function (oxygen absorption function) is obtained. In this specification, the “carbon-carbon double bond” does not include a double bond contained in an aromatic ring. In this specification, the term “double bond” means “carbon-carbon double bond” unless otherwise specified.

  Rather than using a resin in which each double bond is separated by 2 to 5 carbons as the thermoplastic resin (A), a resin in which each double bond is separated by 7 or more carbons is used. When used, the present inventors have found that a decomposition product generated after oxygen absorption has a high molecular weight. By expanding the distance between the double bonds, the decomposed product has a high molecular weight, and the volatility of the decomposed product is lowered. Therefore, it is possible to suppress the generation of odor even after oxygen absorption. On the other hand, if the adjacent carbon-carbon double bonds are separated by more than 13 carbons, the amount of oxygen absorbed per unit weight of the resin composition decreases, which is not preferable from the viewpoint of oxygen absorption.

  The amount of carbon-carbon double bonds contained in the thermoplastic resin (A) is preferably 0.004 mol / g to 0.0085 mol / g, more preferably 0.005 mol / g to 0.0075 mol / g, More preferably, it is 0.006 mol / g-0.007 mol / g. When content of a carbon-carbon double bond is less than 0.004 mol / g, there exists a possibility that the oxygen scavenging function of the resin composition obtained may become inadequate. Moreover, when the said content is 0.0085 mol / g or more, there exists a tendency for the unpleasant odor which a resin composition emits after oxygen absorption increases.

  In a typical thermoplastic resin (A), the carbon-carbon double bond contained in the thermoplastic resin (A) exists substantially only in the unsaturated carbon chain (U) that is the main chain. Here, “the carbon-carbon double bond is substantially present only in the unsaturated carbon chain (U)” means 90 mol% or more of the carbon-carbon double bond contained in the thermoplastic resin (A). Means present in unsaturated carbon chain (U). In this case, even if the double bond or its allylic position is partially oxidized or cleaved by the reaction with oxygen, a low molecular weight fragment is hardly generated as in the case where the double bond in the side chain is cleaved. Therefore, the generation of a low molecular weight decomposition product is extremely small. Some of the low-molecular-weight decomposition products are unpleasant odor substances, and since such decomposition products are not generated, no unpleasant odor is generated. In one example, the carbon-carbon double bond contained in the thermoplastic resin (A) exists only in the unsaturated carbon chain (U).

  In an example of the thermoplastic resin (A), the carbon-carbon double bond contained in the thermoplastic resin (A) is present substantially (for example, completely) only in the unsaturated carbon chain (U) as the main chain. And in unsaturated carbon chain (U), carbon number n of the carbon chain (C) which exists between adjacent carbon-carbon double bonds exists in the said range.

The carbon chain (C) is typically a saturated carbon chain (a chain composed of a plurality of carbon atoms bonded by a single bond). In one example, in the unsaturated carbon chain (U), adjacent carbon-carbon double bonds are connected by a polymethylene group having 7 to 13 carbon atoms. Here, the polymethylene group is represented by the formula — (CH ₂ ) _n —.

In the thermoplastic resin (A), it is particularly preferable that the carbon number n of all the carbon chains (C) is 7 or more. A preferred example of the saturated carbon chain (U) is represented by the following formula (1).

  In the formula (1), the carbon number n of the carbon chain (C) connecting adjacent carbon-carbon double bonds is in the range of 7 to 13 (for example, the range of 8 to 13 or the range of 8 to 10). m represents a natural number (degree of polymerization). In the structure of the formula (1), all the carbon chains (C) have the same carbon number n. The thermoplastic resin (A) may be a ring-opening metathesis polymer of 9 to 15-membered cyclic olefin. Such polymers have the structure of formula (1) where n is in the range of 7-13. For example, when the cyclic olefin is cyclododecene, a polymer having 10 carbon atoms in the formula (1) is obtained.

  There is no particular limitation on the molecular weight of the thermoplastic resin (A). For example, the weight average molecular weight of the thermoplastic resin (A) is preferably in the range of 1,000 to 500,000, and more preferably in the range of 6,000 to 200,000. When the weight average molecular weight is less than 1,000, the low molecular weight component of the resulting thermoplastic resin (A) may be eluted during retort. On the other hand, if the weight average molecular weight is larger than 500,000, molding processability and handling property may be deteriorated.

(1.2) Manufacturing method of thermoplastic resin (A) The manufacturing method of a thermoplastic resin (A) is not specifically limited. The thermoplastic resin (A) may be formed by acyclic diene metathesis polymerization of a chain diene compound or may be formed by ring-opening metathesis polymerization of a cyclic olefin. A polymer having an average carbon number n of less than 7 carbon chains connecting carbon-carbon double bonds is partially hydrogenated (hereinafter referred to as hydrogenation), so that the average carbon number n is 7 It is good also as the range of ~ 13.

  The thermoplastic resin (A) may be formed by acyclic diene metathesis polymerization of a chain diene compound having 11 to 17 carbon atoms having carbon-carbon double bonds at both ends, or a 9-membered ring. It may be formed by ring-opening metathesis polymerization of cyclic olefins having 15 or less members. Among these methods, the method based on ring-opening metathesis polymerization of cyclic olefins is particularly effective because there is no ethylene by-product and the production process is not complicated. In general, in ring-opening metathesis polymerization, a cyclic olefin is polymerized in an inert solvent in the presence of a polymerization catalyst, a chain transfer agent, or the like as necessary. Hereinafter, the preparation of the thermoplastic resin (A) by the ring-opening metathesis polymerization method will be described.

(1.2.1) Cyclic olefin The cyclic olefin having 9 or more carbon atoms, which is a raw material for the thermoplastic resin (A), is not particularly limited, but cyclomonoenes such as cyclononene, cyclodecene, cycloundecene, and cyclododecene are used. be able to. These may have a substituent such as an alkoxy group, a carbonyl group, an alkoxycarbonyl group, or a halogen atom. In view of availability, economy, and use as an oxygen absorbent, cyclododecene is particularly preferred.

(1.2.2) Polymerization catalyst and chain transfer agent Examples of the catalyst for ring-opening metathesis polymerization include a catalyst having a transition metal halide as a main component and a transition metal carbene complex catalyst. The catalyst having a transition metal halide as a main component is a catalyst containing a transition metal halide of a transition metal of Group 4 to 8 of the periodic table as a main component and an organometallic compound other than the transition metal as a promoter.

  The transition metal carbene complex catalyst is a carbene complex compound of a transition metal of Group 4 to 8 of the periodic table. Examples thereof include a tungsten carbene complex catalyst, a molybdenum carbene complex catalyst, a rhenium carbene complex catalyst, and a ruthenium carbene complex catalyst. Is mentioned.

  These ring-opening metathesis polymerization catalysts can be used alone or in admixture of two or more. Among these, it is preferable to use a transition metal carbene complex catalyst because it does not require a cocatalyst and is highly active. Furthermore, the use of a ruthenium carbene complex catalyst is particularly preferable from the viewpoint of the catalyst residue in the polymer.

  Regarding the amount of the catalyst used in the metathesis reaction, the molar ratio of the catalyst to the cyclic olefin monomer subjected to the polymerization reaction is in the range of catalyst: cyclic olefin monomer = 1: 100 to 1: 2,000,000. It is preferably in the range of 1: 500 to 1: 1,000,000, more preferably in the range of 1: 1,000 to 1: 700,000. If the amount of catalyst is too large, it is difficult to remove the catalyst after the reaction, and if it is too small, sufficient polymerization activity may not be obtained.

  The chain transfer agent is not particularly limited, but is α-olefin such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 2-butene, 2-pentene, 2-hexene, 3-hexene. Internal olefins such as 2-heptene, 3-heptene, 2-octene, 3-octene and 4-octene can be used. These may have a substituent such as a hydroxyl group, an alkoxy group, an acyl group, a carbonyl group, an alkoxycarbonyl group, or a halogen atom. These may be used alone or in combination.

  The amount of the chain transfer agent used is not particularly limited as long as it is an amount capable of producing a polymer having a sufficient molecular weight in the polymerization reaction. For example, the molar ratio of cyclic olefin to chain transfer agent may be in the range of cyclic olefin: chain transfer agent = 1,000: 1 to 20: 1, preferably in the range of 800: 1 to 50: 1. It is in.

  The thermoplastic resin (A) may be produced by partially hydrogenating a polymer in which the carbon number n of the carbon chain connecting the carbon-carbon double bonds is 7 or less. Such a polymer may be formed by acyclic diene metathesis polymerization of a chain diene compound having less than 11 carbon atoms having a carbon-carbon double bond at both ends, or a cyclic olefin having less than 9 carbon atoms. You may form by ring-opening metathesis polymerization. The hydrogenation reaction can be carried out by a known method. For example, Raney nickel; heterogeneous catalyst in which a metal such as Pt, Pd, Ru, Rh, Ni is supported on carbon, alumina, diatomaceous earth, etc .; transition metal compound and alkyl Ziegler catalyst consisting of a combination with aluminum compound, alkyl lithium compound, etc .; in the presence of hydrogenation catalyst such as metallocene catalyst, reaction and reaction with hydrogen by dissolving polymer in solvent inert to hydrogenation catalyst Can be performed.

(2) Transition metal salt (B)
The transition metal salt (B) has an effect of improving the oxygen scavenging function of the resin composition by promoting the oxidation reaction of the thermoplastic resin (A). By using the transition metal salt (B), the oxygen scavenging function of the packaging material using the resin composition of the present invention is improved. For example, by using the transition metal salt (B), the oxygen gas present inside the packaging material using the resin composition of the present invention and the oxygen gas which is to permeate the packaging material and the thermoplastic resin (A) are used. The reaction is promoted.

  Examples of the transition metal contained in the transition metal salt (B) include, but are not limited to, iron, nickel, copper, manganese, cobalt, rhodium, titanium, chromium, vanadium, and ruthenium. Among these, iron, nickel, copper, manganese, and cobalt are preferable, manganese and cobalt are more preferable, and cobalt is more preferable.

  Examples of the counter ion of the metal contained in the transition metal salt (B) include an anion derived from an organic acid or chloride. Examples of the organic acid include acetic acid, stearic acid, acetylacetone, dimethyldithiocarbamic acid, palmitic acid, 2-ethylhexanoic acid, neodecanoic acid, linoleic acid, toluic acid, oleic acid, resin acid, capric acid, and naphthenic acid. However, it is not limited to these. Particularly suitable salts include cobalt 2-ethylhexanoate, cobalt neodecanoate and cobalt stearate. The metal salt may be a so-called ionomer having a polymeric counter ion.

  The transition metal salt (B) is preferably contained in the composition at a ratio of 1 to 50,000 ppm in terms of metal element based on the mass of the thermoplastic resin (A). The transition metal salt (B) is more preferably contained in the range of 5 to 10,000 ppm, more preferably in the range of 10 to 5,000 ppm. As described later, when the resin composition of the present invention contains a matrix resin (M) in addition to the thermoplastic resin (A), the transition metal salt (B) is preferably a thermoplastic resin ( A) and a matrix resin (M) are contained in a proportion of 1 to 50,000 ppm in terms of metal elements based on the total mass. When the content of the transition metal salt (B) is less than 1 ppm, the oxygen absorption effect of the resin composition may be insufficient. On the other hand, when the content of the transition metal salt (B) exceeds 50,000 ppm, the thermal stability of the resin composition is lowered, and the generation of decomposition gas and the generation of gels and bumps may increase.

  The resin composition of the present invention may be composed only of the thermoplastic resin (A) and the transition metal salt (B), or may contain other substances in addition to them. Examples of other substances include resins other than the thermoplastic resin (A) (matrix resin (M) described later), antioxidants, and deodorizers. However, it is not preferable to use a substance that causes a large amount of unpleasant odor as another substance.

(3) Matrix resin (M)
The resin composition of the present invention may contain a matrix resin (sometimes referred to as “matrix (C)” in this specification) as necessary. The matrix resin (M) has a function as a support for diluting or dispersing the thermoplastic resin (A). The matrix resin (M) has a function of imparting the resin composition with the properties of the matrix resin (M). The matrix resin (M) is appropriately selected according to the purpose of use of the composition. For example, when it is desired to impart gas barrier properties to the composition of the present invention, a gas barrier resin is used as the matrix resin (M). When a predetermined molded body (such as a container) is formed using a composition containing a gas barrier resin, the gas barrier resin suppresses oxygen gas outside the molded body from passing through the molded body.

As the gas barrier resin used as the matrix resin (M), a resin having an oxygen permeation rate of not more than 500 ml · 20 μm / (m ² · day · atm) at 20 ° C. and 65% RH is suitably used. This oxygen permeation rate was measured in an environment of 20 ° C. and relative humidity 65%, and the oxygen permeation per day through a film having an area of 1 m ² and a thickness of 20 μm with a differential pressure of oxygen of 1 atm. It means that the volume is 500 ml or less. If a resin having an oxygen transmission rate exceeding 500 ml · 20 μm / (m ² · day · atm) is used, the gas barrier effect may be insufficient. The oxygen permeation rate of the gas barrier resin is more preferably 100 ml · 20 μm / (m ² · day · atm) or less, further preferably 20 ml · 20 μm / (m ² · day · atm) or less, It is preferably 5 ml · 20 μm / (m ² · day · atm) or less. By using both the gas barrier resin and the thermoplastic resin (A), an oxygen scavenging effect is exhibited in addition to the gas barrier effect, and as a result, a resin composition having an extremely high gas barrier property can be obtained.

  Typical examples of the gas barrier resin include polyvinyl alcohol resins, polyamide resins, polyvinyl chloride resins, polyacrylonitrile resins, and the like, but the gas barrier resins are not limited to these resins. Note that it is not preferable to use a large amount of a resin that causes unpleasant odor as a gas barrier resin. For example, it is not preferable to use a large amount of a resin containing a plurality of carbon-carbon double bonds bonded by carbon chains having 6 or less carbon atoms as the gas barrier resin. Therefore, it is preferable that the resin composition of this invention does not contain such resin substantially.

(Use of resin composition)
By forming a molded body (for example, a packaging material) using the resin composition of the present invention, various molded bodies having high oxygen absorbability can be obtained. Examples of such a molded body include a multilayer film, a multilayer container, a cap and the like including a layer made of the resin composition. The resin composition of the present invention is particularly suitably used for a container for storing articles (for example, food cosmetics) that are susceptible to deterioration by oxygen and in which fragrance is important. Moreover, the resin composition of this invention is used suitably also as packaging materials, such as foodstuffs which require a retort process. Furthermore, since the resin composition of the present invention has a high oxygen scavenging function, it is also useful as an oxygen absorbent that is easy to handle.

  The packaging material of the present invention includes a layer made of the resin composition of the present invention. Below, the layer which consists of a resin composition of this invention may be called "layer (Y)." A typical example of the packaging material of the present invention is a laminated film of a layer (Y) and another layer (film). Such a laminated film can be formed, for example, by laminating or coextrusion of the layer (Y) and another layer. There is no limitation on the laminating method, and a known method may be used. For example, a method using an adhesive or a method using a molten resin can be employed.

  The packaging material of the present invention may be a molded packaging material, and may be, for example, a container, a bag, or a lid molded into a predetermined shape. Examples of the packaging material of the present invention include a retort packaging material such as a retort pouch.

  When the packaging material of this invention is a laminated film, what is necessary is just to select the thickness of each layer and the kind of other layer laminated | stacked with a layer (Y) according to the characteristic calculated | required by a laminated film. Examples of other layers to be laminated include a polyolefin layer, a polyamide layer, a polyester layer, and the like. Moreover, you may provide the layer using collection | recovery resin which consists of scraps, such as a trim generated at the time of shaping | molding.

  Examples of the present invention will be specifically described below, but the present invention is not limited thereto. Analysis and evaluation in the following examples and comparative examples were performed as follows.

(1) Molecular structure and hydrogenation rate of thermoplastic resin (A) The molecular structure and hydrogenation rate (only synthesis example 4) of thermoplastic resin (A) are obtained by ¹ H-NMR (nuclear magnetic resonance) measurement. Determined from spectra.
<Measurement conditions>
Device: JNM-GX-500, manufactured by JEOL Ltd. Observation frequency: 500 MHz
Solvent: Deuterated orthodichlorobenzene Temperature: 100 ° C

<Analysis method>
The chemical shift value was based on the TMS peak of 0 ppm. Integral value A of proton peak derived from 5.65 ppm double bond, integral value B of proton peak of 1.55 ppm methylene (excluding allyl hydrogen), proton peak of 2.25 ppm methylene (allyl hydrogen) From the integral value C, the double bond amount of the thermoplastic resin was calculated.

Moreover, the hydrogenation rate was calculated from the following formula using the integrated values A, B and C.
Hydrogenation rate (%) = ((B + C) / A-6) / ((B + C) / A + 2) × 100

(2) Weight average molecular weight of thermoplastic resin (A) The weight average molecular weight of the thermoplastic resin (A) was measured by gel permeation chromatography (GPC) and expressed as a polystyrene equivalent value.
<Measurement conditions>
Apparatus: Waters Gel Permeation Chromatography (GPC) V2000
Column: HT-806M (× 2) (trade name: Shodex) (column temperature: 90 ° C.)
Mobile phase: orthodichlorobenzene (o-DCB) (flow rate: 1.0 ml / min)
Detector: RI
Standard: Polystyrene

Synthesis Example 1 Synthesis of Polycyclododecene After replacing a 5-liter glass three-necked flask equipped with a stirrer and a thermometer with dry nitrogen gas, 166 g (1.0 mol) of cyclododecene was added thereto. -183 mg (1.7 mmol) of vinyl-1-cyclohexene was added and dissolved in 624 g of heptane.

  Next, a catalyst solution was prepared by dissolving 8.48 mg (10 μmol) of benzylidene (1,3-dimesitylimidazolidine-2-ylidene) (tricyclohexylphosphine) ruthenium dichloride in 1 g of toluene. This catalyst solution was quickly added to the above heptane solution, and ring-opening metathesis polymerization was performed at 70 ° C. When analyzed by gas chromatography (manufactured by Shimadzu Corp., GC-14B; column: G-100, manufactured by Chemicals Inspection Association) 5 minutes after the start of polymerization, 4-vinyl-1-cyclohexene had disappeared. In this way, ring-opening metathesis polymerization of cyclododecene was performed.

  After adding methanol 600g to the obtained reaction liquid, stirring for 30 minutes at 40 degreeC, and also liquid-separating by leaving still at 40 degreeC for 1 hour, the lower layer (methanol layer) was removed. To the remaining upper layer (heptane layer), 600 g of methanol was added again, and the mixture was stirred at 40 ° C. for 30 minutes and allowed to stand at 40 ° C. for 1 hour, and then the lower layer (methanol layer) was removed. Heptane was distilled off from the remaining upper layer (heptane layer) under reduced pressure. The resulting reaction product was then dried for 24 hours at 50 Pa and 40 ° C. using a vacuum dryer. Thus, 132.8 g (yield 80%) of a polymer having a weight average molecular weight of 100,000 was obtained.

(Synthesis Example 2) Synthesis of polycyclodecene Except that the monomer was changed to 138 g (1.0 mol) of cyclodecene, the same operation as in Synthesis Example 1 was performed, and 114.5 g (yield) of a polymer having a weight average molecular weight of 107,400. 83%).

(Synthesis Example 3) Synthesis of polycyclooctene 96.8 g of a polymer having a weight average molecular weight of 189,900 was carried out in the same manner as in Synthesis Example 1 except that the monomer was changed to 110 g (1.0 mol) of cyclooctene. Yield 88%).

  The polycyclododecene, polycyclodecene, and polycyclooctene synthesized in Synthesis Examples 1 to 3 are considered to have the structure of the formula (1) from the starting materials, synthesis methods, and analysis results. Specifically, polycyclododecene, polycyclodecene, and polycyclooctene are considered to have structures in which n in formula (1) is 10, 8, and 6, respectively.

(Synthesis Example 4) Synthesis of hydrogenated polycyclooctene 40 g of the polycyclooctene obtained in Synthesis Example 3 was placed in a 1.3 L autoclave and dissolved in cyclohexane (687 g). Next, the inside of the container is purged with nitrogen, and a hydrogenation reaction is performed by adding a reaction product of nickel octylate and triisobutylaluminum as a hydrogenation catalyst to the resulting solution and introducing hydrogen gas into the autoclave. It was. This operation was repeated to achieve the desired hydrogenation rate, and then the reaction was stopped using an aqueous citric acid solution and H ₂ O ₂ . The obtained reaction product was reprecipitated with methanol, and then dried under reduced pressure overnight at 40 ° C. In this way, 36 g (90% yield) of hydrogenated polycyclooctene was obtained. When the molecular structure of the obtained hydrogenated polycyclooctene was measured by the above method, the hydrogenation rate was 36%, and it had a structure in which adjacent double bonds were separated by an average of 10 carbons. .

Example 1
100 parts by mass of polycyclododecene obtained in Synthesis Example 1 and 0.42 parts by mass of cobalt (II) stearate (400 ppm as cobalt atoms) were dry-blended, and a roller mixer (LABO PLASTOMIL MODEL R100 manufactured by Toyo Seiki Co., Ltd.) A lump mixture was obtained by melt-kneading for 5 minutes. The melt-kneading was performed under the conditions of 190 ° C., screw rotation speed 60 rpm, and total resin amount 70.59 g while purging the inside of the chamber with nitrogen. The obtained lump was cut into pellets to obtain pellets of a resin composition composed of polycyclododecene and cobalt stearate.

  The obtained pellet was pulverized using an ultracentrifugal pulverizer (ZM100 manufactured by Retsch). Next, the pulverized product was sieved to recover a powder of 100 μm or less. 20 mg of the obtained powder was placed in a 20 ml internal volume vial filled with 50% RH air at 23 ° C. and left in a 60 ° C. incubator for 3 days. And the gas component of the head space of the sample after standing for 3 days was quantified by gas chromatograph mass spectrometry (GC-MS). The measurement conditions for GC-MS are as follows.

Thermal desorption device: Headspace sampler JHS-100A (manufactured by Nihon Analytical Industries, Ltd.)
Resorption temperature: 320 ° C., 25 seconds MS apparatus: JMS SX102A mass spectrometer (manufactured by JEOL Ltd.)
Data processing: MS-MP7000 data processing system (manufactured by JEOL Ltd.)
GC device: HP5890 (manufactured by Hewlett-Packard)
Carrier gas: Helium 20 ml / min Column: Pora PROT Q 25m × 0.32mmID
Column temperature: 80 ° C. to 250 ° C. (heating rate 8 ° C./min)
Inlet temperature: 270 ° C
Separator temperature: 270 ° C

A calibration curve is created by dissolving a predetermined amount of butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid in hexane, storing at 60 ° C, and collecting the generated gas did. The amount of gas generated per unit mass of the measurement sample was calculated by the following equation.
Generated gas amount (ppm = μg / g) = generated gas amount (μg) / charged sample amount (g)

(Example 2)
A powder was prepared in the same manner as in Example 1 except that the polycyclodecene obtained in Synthesis Example 2 was used instead of polycyclododecene, and the same method as in Example 1 was performed using the powder. The evolved gas was analyzed.

(Example 3)
A powder was prepared in the same manner as in Example 1 except that the hydrogenated polycyclooctene obtained in Synthesis Example 4 was used instead of polycyclododecene, and the powder was used as in Example 1. The generated gas was analyzed by the method.

(Comparative Example 1)
A powder was prepared in the same manner as in Example 1 except that the polycyclooctene obtained in Synthesis Example 3 was used instead of polycyclododecene, and the same method as in Example 1 was performed using the powder. The evolved gas was analyzed.

(Odor evaluation)
0.02 g of the powder obtained in Examples 1 to 3 and Comparative Example 1 was placed in a bottle with an internal capacity of 85 ml filled with 50% RH air at 23 ° C. and stored for 3 days. Thereafter, five panelists evaluated the sample headspace gas according to the following criteria, and determined the average. The smaller the evaluation score, the less the odor.
The smell is not felt at all. Evaluation score 0
Smell is felt slightly ... Evaluation point 1
A little acid odor can be felt ... Evaluation point 2
The acid odor is strong ........ Evaluation score 3

(Oxygen absorption evaluation)
0.02 g of the powder obtained in Examples 1 to 3 and Comparative Example 1 was sealed in a bottle with an internal volume of 85 ml that had been filled with 50% RH air at 23 ° C. Thereafter, the oxygen concentration in the bottle was measured at regular intervals, and the amount of absorbed oxygen was calculated.

  Table 1 shows the thermoplastic resin (A) used and the measurement results for Examples 1 to 3 and Comparative Example 1.

  As shown in Table 1, in the resin compositions of Examples 1 to 3, the generation amount of low molecular weight odor substances such as valeric acid and hexanoic acid was small. The resin compositions of Examples 1 to 3 had lower odor than the resin composition of Comparative Example 1. Among Examples 1 to 3, the resin composition of Example 1 using polycyclododecene had particularly low odor. In addition, the resin compositions of Examples 1 to 3 sufficiently had an oxygen absorbing ability as an oxygen absorbent.

Example 4
8 parts by mass of polycyclododecene obtained in Synthesis Example 1, 0.42 parts by mass of cobalt stearate (400 ppm as cobalt atoms) and 92 parts by mass of EVOH were dry-blended, and a roller mixer (LABO manufactured by Toyo Seiki Co., Ltd.) A block-like mixture was obtained by melt-kneading for 5 minutes using PLASTOMIL MODEL R100). The melt-kneading was performed under the conditions of 190 ° C., screw rotation speed 60 rpm, and total resin amount 70.59 g while purging the inside of the chamber with nitrogen. The obtained lump was cut into pellets to obtain pellets of a resin composition composed of polycyclododecene, cobalt stearate, and EVOH. The obtained resin composition was heated to 200 ° C. and pressed to obtain a film having a thickness of about 200 μm.

  A stretched polypropylene film (OP- # 20 U-1 manufactured by Tosero Co., Ltd.) having a thickness of 20 μm was laminated on both surfaces of the film using an adhesive. For the adhesive, urethane adhesive (product name: AD335A, manufactured by Toyo Morton) and curing agent (product name: Cat-10, manufactured by Toyo Morton), toluene / methyl ethyl ketone mixed solution (weight ratio 1: 1) and Was used. In this way, a laminated sheet having a layer configuration of stretched polypropylene film layer / urethane adhesive layer / resin composition layer (oxygen-absorbing film layer) / urethane adhesive layer / stretched polypropylene film layer was prepared.

Next, the two laminated sheets obtained were overlapped and heat-sealed to produce a 30 cm × 30 cm pouch. Water was put inside the pouch. The pouch was stored for 60 days at 30 ° C. in an atmosphere of 80% RH. And 5 panelists taste-evaluated the water inside the pouch after storage according to the following criteria, and the average was calculated | required. The smaller the evaluation score, the less the unpleasant taste.
No unpleasant taste ... Evaluation score 0
Unpleasant taste to be slightly ... Evaluation point 1
A little unpleasant taste ... Evaluation point 2
Unpleasant taste is strong ... Evaluation point 3

(Example 5)
A pouch was prepared and evaluated in the same manner as in Example 4 except that the polycyclodecene obtained in Synthesis Example 2 was used instead of polycyclododecene.

(Example 6)
A pouch was prepared and evaluated in the same manner as in Example 4 except that the hydrogenated polycyclooctene obtained in Synthesis Example 4 was used in place of polycyclododecene.

(Comparative Example 2)
A pouch was prepared and evaluated in the same manner as in Example 4 except that the polycyclooctene obtained in Synthesis Example 3 was used instead of polycyclododecene.

  About Examples 4-6 and the comparative example 2, the used thermoplastic resin (A) and an evaluation result are shown.

  As shown in Table 2, the packaging materials of Examples 4 to 6 were higher in evaluation than the packaging material of Comparative Example 2. Among Examples 4-6, the packaging material using polycyclododecene was particularly highly evaluated.

  As described above, according to the present invention, it is possible to obtain a resin composition having excellent oxygen absorbability and generating less unpleasant odor due to oxygen absorption. Furthermore, according to the present invention, in addition to the above performance, an oxygen-absorbing resin composition can be obtained that generates less unpleasant odor even when subjected to treatment with hot water such as retort treatment.

  The present invention can be used for resin compositions and various articles (molded articles, packaging materials, oxygen absorbents, etc.) using the same.

Claims (9)

An oxygen-absorbing resin composition comprising a thermoplastic resin and a transition metal salt,
The thermoplastic resin includes an unsaturated carbon chain containing a plurality of carbon-carbon double bonds as a main chain,
The said thermoplastic resin WHEREIN: The resin composition whose average of the number of the carbon atoms which exist between adjacent carbon-carbon double bonds exists in the range of 7-13.   The resin composition according to claim 1, wherein a carbon-carbon double bond contained in the thermoplastic resin is present only in the unsaturated carbon chain.   The resin composition according to claim 1 or 2, wherein in the unsaturated carbon chain, adjacent carbon-carbon double bonds are connected by a polymethylene group having a carbon number of 7 to 13.   The resin composition according to any one of claims 1 to 3, wherein the thermoplastic resin is a ring-opening metathesis polymer of a cyclic olefin having 9 to 15 members.   The resin composition according to claim 4, wherein the cyclic olefin is cyclododecene.   The resin composition according to any one of claims 1 to 5, further comprising a matrix resin. The resin composition according to claim 6, wherein the matrix resin is a resin having an oxygen transmission rate at 20 ° C. and 65% RH of 500 ml · 20 μm / (m ² · day · atm) or less.   The packaging material containing the layer which consists of a resin composition of any one of Claims 1-7.   The packaging material according to claim 8, which is a packaging material for retort.